Hi,
The P0720 indicates the output speed sensor isn't working. That is the likely cause of the speedo issue.
The P2106 is part of the FMEM system (failure mode effects management). This is a strategy that is used by the powertrain control module to maintain operation in the event of a sensor failure. When a sensor input is identified as out-of-limits by the PCM, an alternative strategy is initiated. Basically, the PCM does adapt to maintain drivability. In this situation, many times it is referred to as limp mode.
The code, P2106, is specific to the TAC (throttle actuator control) system. This again can tie into the lean mixture or drivability issues, but not the transmission concerns you described.
Here is the interesting thing. You mentioned the vehicle is running lean. When the FMEM controls engine management, it usually puts it in a rich mixture. If it is lean, that is an indicator that there may be a large engine vacuum leak or low fuel pressure. So, I need to know if these are the only two codes you retrieved.
Now, the idea that the output speed sensor has likely failed would normally cause rough or delayed shift points, the speedometer not to work, and the vehicle being placed into limp mode, but I'm struggling to see how it would prevent forward movement.
With all of that, I need to know if other codes are present, the lean mixture code you have, if you have a live data scan tool, and if your scanner is able to read can-bus codes.
There is one thing you can check. The output speed sensor is on the left side (driver's side) of the transmission. Check the wiring and connector for damage, corrosion, and make sure the connector is tight. See pic 1 below for the location.
Let me know if you have other codes and if you confirmed the transmission fluid is clean and full.
Take care,
Joe
See pic below.
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Monday, December 27th, 2021 AT 7:24 PM
